When sharing a transmission bandwidth from an optical network unit (ONU) to an optical line terminal (OLT) for a plurality of ONUs or service paths, as a scheme for dynamically allocating bandwidths according to the bandwidth contracted by each request source, a scheme is proposed in which a bandwidth allocation is determined, based upon information related to the cumulative value of bandwidth allocation sizes which have been allocated in the past.
The topology of such a conventional scheme is shown in FIG. 7. An optical fiber 100 which is connected to a single optical line terminal (OLT) 120 is branched by an optical branching section 101 into a plurality of fibers 100a, 100b, and 100c, and these are connected to an optical network unit (ONU) 111, 112, and 113, respectively.
Each of the ONUs 111, 112, and 113 notifies a request data size to the OLT 120. On each cycle and for each of the ONUs, for example, a dynamic bandwidth allocation circuit 121 which is provided inside the OLT 120 calculates a target data size by apportioning the ideal total allocated bandwidth proportionally according to the contracted bandwidth; calculates the excess allocated data size from the cumulative value of the difference between the allocated data size of each cycle up to the previous cycle and the target data size; and determines the bandwidth allocation for the next cycle based upon the excess allocated data size and the request data size (for example, refer to Patent Document 1).
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2003-087283